Treatment of mineral oils



Patented Nov. 26, 1946 I TREATMENT OF mnpngno ps Lawton A. Burrows, Woodbury,=N.J., 'assigno'r to E. I. duPont de Nemours & Company, Wilmington, Del., a corporation of Delaware 7 g No Drawing. Application June 15, 1945 Serial No. 599,745

6 Claims. (01. 19,

This invention relates to a novel method of treating and refining mineral oils and more particularly to a method of dewaxing such oils.

The problem of separating wax-like constituents from mineral oils has assumed much importance to the petroleum industry in recent years. The methods proposed and applied for accomplishing this result have in general comprised (1) cooling of the liquid oil, with crystallization of the wax at the low temperatures obtained, (2) the use of solvents for selective solution of: certain ingredients and the separation of the oil into two distinct layers, or (3) the com-' bination of selective solvents and refrigeration. The last method has been the one'most successfully applied. In all procedures, the waxy constituents have been separated from the body of the mineral oil and, where present, the solvent has been removed. While various solvents have been used, the results have not been completely satisfactory because of the difficulty of finding a solvent possessing all the desirable characteristics.

An object of the present invention is a, new and improved method of treating mineral oils and separating various constituents, in order to obtain a refined product. A further object is such a method, which employs for the purpose a solvent of superior properties. A still further object is a method of dewaxing mineral oils. Additional objects will be disclosed as the invention is described more at length in the following.

I have found that the foregoing objects are attained when the mineral oil for treatment is admixed with nitrocyclohexane and maintained at a sufficiently elevated temperature to assure substantial solution or miscibility, and the solution is then cooled to a temperature at which segregation into more than one portion results. The segregated portions are separated and the nitrocyclohexane recovered from the respective portions, preferably by distillation under reduced pressure. In the dewaxing of oils, the wax portion will ordinarily precipitate out in solid form on cooling and will be separated from the oil by filtration, centrifuging, or like procedures.

The following will serve as a specific example of a procedure for carrying out the invention. This is, of course, merely illustrative and is not to betaken as limiting in any way.

A sample of Pennsylvania wax distillate was used, having a pour point of 105 F. and a viscosity of 60 Saybolt Universal seconds at 210 F. The oil was mixed with nitrocyclohexane in the proportion of 30 to 70 respectively, and a temperature of F. was maintained, at which temperature complete solution had resulted. The solution was then allowed to cool for one hour at a temperature of around 32-37 R, where precipitation of wax resulted. The solution was filtered, and the wax removed was transferred to another vessel, from which the nitrocyclohexane was removed by evaporation. The filtrate was transferred to a flask and the nitrocyclohexane distilled off under 15 mm. pressure. The pour point of the recovered oil Was 45 F. The amount of wax separated from the oil was 11.5%.

A similar procedure in which use was made of a two-component solvent commonly used in oil refining gave a pour point for the recovered oil of 50 F. and a wax removal of 10%.

Nitrocyclohexane from the process described is recovered in large part and can be used repeatedly in successive operations, without removal of small amounts of hydrocarbon. Eventually purification of the repeatedly used solvent may be necessary.

The employment of nitrocyclohexane for purposes of .wax removal has been emphasized in the foregoing, and it is this use which is particularly important. The invention will include, however, selective separation of any ingredients by means of nitrocyclohexane. It may be desired,'for example, to separate mineral oils into portions richer respectively in parafiin or naphthenic hydrocarbons, and my invention is intended to cover such a process. Moreover, in addition to the removal of waxes by refrigeration of the solution in nitrocyclohexane and precipitation of the Waxy constituents, the separation may be into two liquid layers, one higher than the other in wax content, rather than separation of a. solid from a liquid. It will be understood,

therefore, that the invention covers all procedures whereby selective extraction and concentration are effected by use of the solvent described. Whereas, also, the example has cited a single batch extraction of the wax content of the oil, it will frequently be desirable to employ a multiple extraction process, wherein fresh sol vent is caused to obtain extractable material from rafiinates from previous extractions. It will be appreciated that the process described isan effective method of decreasing the pour point of oils.

Nitrocyclohexane is excellently adapted for use in the dewaxing of oils because of its properties as a solvent, being miscible in all proportions with such other solvents as ethanol, ether, acetone, benzene, kerosene, and the like. While it has been disclosed as the sole solvent in extras tive dewaxing processes, it may if desired be used in accompaniment with other solvents; such as, nitrobenzene, benzene, and the like.

It will be understood, therefore, that I intend to be limited only by the following claims.

I claim: I

1. The process of treating mineral oils and separating various constituents therein contained, which comprises mixing the mineral oil with nitrocyclohexane and effecting substantial solution therebetween, cooling the solution to a temperature at which segregation into more than one portion results, and separating said segregated portions.

2. The process of claim 1, in which two layers of liquid are formed on cooling of the solution.

3. The process of claim 1, in which solidification of a. portion of the mineral 011 takes place on cooling.

4. The process of refining mineral oils and separatlng wax therefrom, which comprises efiecting substantial solution of said oil in nitrocyclohexane at a temperature sufliciently elevated therefor, cooling said solution to a temperature at which separation of the wax in solid form takes place, and removing the separated solid from contact with substantially the bulk of the solution.

5. The method of claim 4, in which the nitrocyclohexane is recovered from the respective liquid and solid separated portions.

6. The method of claim 4, in which the nitrocyclohexane is removed from the respective portions by distillation under reduced pressure.

LAWTON A. BURROWS. 

